Improvement in methods of tanning



UNITED STATES PATENT OFFICE.

MARTIN A. BELL, OF RUSHFORD, NEW YORK.

IMPROVEMENT IN METHODS OF TANNING.

Specification forming part of Letters Patent No. 27,96l, dated April 24, 1860.

To all whom it may concern:

Beit known thatI, MARTINA. BELL, of Bushford, in the county of Allegany and State of New York, have invented certain new and useful Improvementsin Tanning Hides and Skins; and I do hereby declare that the following is a full, clear, and exact description of my mode of tanning.

The nature of my invention consists in the use of lye with tannic acid, as will be hereinafter set forth.

I remove the hair from the hides and skins and prepare them for tanning by any of the methods now in use. I then immerse them in the tannin liquor and handle them from two to four days.

The tannin liquor or compound in which the skins are immersed is made in the following manner: I take one bushelof wood ashes, stir it well in fifty gallons of water, and then let it settle. I then draw off forty gallons of the lye thus made and add to it forty pounds of terra-japonica, place them in a copper vessel, boil them until the terra-ja-ponica is all dissolved, then allow them to cool partially, and the solution is ready for use. For some kinds of leather I use forty gallons of the lye, forty pounds of terra-japonica, ten pounds of alum, and six pounds of common salt. These ingredients are then boiled in a copper pan and then allowed to cool partially. When cooled sufliciently the hides are immersed in the solution and handled, as stated, from two to four days.

The solution should be kept warm all the while. Its temperature should never be allowed under blood-heat when in use. If the temperature is reduced much below bloodheat the potash of the lye may precipitate the alumina of the alum, which, having a strong affinity for the tannic acid, may carry a portion of it down with it, and thus destroy the effect of the solution. It is all important that the solution should be kept moderately warm,

and the temperature above stated is that which I mostly prefer, though a little higher temperature will do no harm. Whenever the latter solution becomes reduced in strength I strengthen by adding to it twenty gallons of water which has been mixed with one bushel of ashes, and with the full amount of the other mentioned ingredients.

Lime has been used in connection with the ingredients herein mentioned in place of the lye but there are many difficulties attending its use for tanning purposes-the liquor is liable to and often does sour, the strength of the liquor cannot be varied, and it cannot be retained without an accumulation of more than is necessary and without great trouble.

By the use of the lye in the manner herein stated the liquor is prevented from becoming sour and may be retained any desired length of time. The strength of the liquor may be varied, as the lye may be made stronger or milder. For making hard leather the lye is made stronger than that indicated and more tannic acid is used, and for making soft and pliable leather the lye is made milder. Thus the strength of the liquor may not only be varied, but the quality of the leather mayalso be varied. Bystrengtheningtheliquorthesamedifficulty of accumulation is not experienced, as is the case with thelime. By the useofthisliquor a greater body and more density is given to the leatherthanisthecasewhenitistannedbyother processes. By being able to vary the strength of the lye I am enabled to use more tannic acid than I could with the lime. Hence I am enabled to tan leather in much shorter time than it is possible to do where lime is used.

I do not consider alum and salt necessary ingredients for tanning purposes generally. I use ordinarily only the lye combined with the tannic acid, the acid being stronger or milder in proportion to the amount oflye used. When the leather is removed from the solution it is ready for use without subjecting it to any other process or manipulation.

I do not lay any claim to the preparation of tannate of potash or soda, as indicated in the patents granted to Obediah Rich in 1856; but

Having thus fully described my invention, what I claim as new, and desire to secure by Letters Patent, is-

Oombining lye with ,tannic acid in substantiall y the proportions herein mentioned,whereby I am enabled to prevent the tanning-liquors from becoming decomposed or sour, am enabled to strengthen them without accumulating more than necessary, and can tan skins in shorter time and with less labor than by any other known process.

MARTIN A. BELL.

Witnesses:

A. H. NOBLE, I. I. BELL. 

